This invention relates to railroad cars. More particularly, it relates to railroad cars with coupling arrangements convertible between conventional coupler and semi-permanent drawbar connections.
Recent concerns for economy in freight transportation have spurred development of a variety of new concepts in railroad rolling stock. These developments include new types of intermodal or trailer-on-flat car arrangements, as well as dual mode vehicles suitable for highway and rail travel.
Lightweight skeletal flatcars have been developed which are sized to carry one semi-trailer. To further minimize weight per axle and maximize productive tonage, such cars have been connected to form multi-platform cars with shared wheel trucks or bogies. Two or more, and as high as ten platforms have been linked through semi-permanent couplings to form a unit. Conventional trucks are disposed at the free ends of the first and last car. Intermediate car ends share a common truck. Examples are the "ten pack" cars operated by the Santa Fe Railroad. U.S. Pat. No. 4,233,909 shows such an arrangement.
A disadvantage of a multi-platform car of the type described is that the cars are not divisible into smaller units. Usage is therefore restricted to applications which insure full loading, such as special purpose unit trains having a specific route and schedule. Another disadvantage arises when repairs are required to one or more of the connected platforms. The entire coupled unit must be removed from service until repairs are completed.
An alternate form of economical intermodel car utilizes single axle trucks at each end of a platform to provide independent status and yet minimize per axle empty weight. These platforms may be coupled together in a conventional way, or in multiples of platforms with semi-permanent couplings to form a multi-platform unit. Examples of such platforms are found in U.S. Pat. No. 4,339,996.
Though most versatile, conventionally coupled cars present a certain weight disadvantage. Semi-permanent connections of cars with single axle trucks, of course, present disadvantages common to other forms of multi-platform car units.
The present invention is directed to providing a car with single axle trucks that possess flexibility to be utilized either as a conventional single platform car, or as a component of a multi-platform car having semi-permanent couplings between platforms.